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Title: Simultaneous Detection of Water, Methane, and Carbon Monoxide in the Atmosphere of Exoplanet HR 8799 b

Here, absorption lines from water, methane, and carbon monoxide are detected in the atmosphere of exoplanet HR 8799 b. A medium-resolution spectrum presented here shows well-resolved and easily identified spectral features from all three molecules across the K band. The majority of the lines are produced by CO and H 2O, but several lines clearly belong to CH 4. Comparisons between these data and atmosphere models covering a range of temperatures and gravities yield log mole fractions of H 2O between –3.09 and –3.91, CO between –3.30 and –3.72, and CH 4 between –5.06 and –5.85. More precise mole fractions are obtained for each temperature and gravity studied. A reanalysis of H-band data, previously obtained at a similar spectral resolution, results in a nearly identical water abundance as determined from the K-band spectrum. The methane abundance is shown to be sensitive to vertical mixing and indicates an eddy diffusion coefficient in the range of 10 6–10 8 cm 2 s –1, comparable to mixing in the deep troposphere of Jupiter. The model comparisons also indicate a carbon-to-oxygen ratio (C/O) between ~0.58 and 0.7, encompassing previous estimates for a second planet in the same system, HR 8799 c. Super-stellar C/O couldmore » indicate planet formation by core-accretion; however, the range of possible C/O for these planets (and the star) is currently too large to comment strongly on planet formation. More precise values of the bulk properties (e.g., effective temperature and surface gravity) are needed for improved abundance estimates.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Univ. of Arizona, Tucson, AZ (United States)
  2. Univ. of California San Diego, La Jolla, CA (United States); Univ. of Toronto, Toronto, ON (Canada)
  3. Stanford Univ., Stanford, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. NRC Herzberg Astronomy and Astrophysics, Victoria, BC (Canada)
Publication Date:
Report Number(s):
LLNL-JRNL-678571
Journal ID: ISSN 1538-4357
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 804; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; brown dwarfs; planetary systems; stars: atmospheres; stars: low-mass
OSTI Identifier:
1367960

Barman, Travis S., Konopacky, Quinn M., Macintosh, Bruce, and Marois, Christian. Simultaneous Detection of Water, Methane, and Carbon Monoxide in the Atmosphere of Exoplanet HR 8799 b. United States: N. p., Web. doi:10.1088/0004-637X/804/1/61.
Barman, Travis S., Konopacky, Quinn M., Macintosh, Bruce, & Marois, Christian. Simultaneous Detection of Water, Methane, and Carbon Monoxide in the Atmosphere of Exoplanet HR 8799 b. United States. doi:10.1088/0004-637X/804/1/61.
Barman, Travis S., Konopacky, Quinn M., Macintosh, Bruce, and Marois, Christian. 2015. "Simultaneous Detection of Water, Methane, and Carbon Monoxide in the Atmosphere of Exoplanet HR 8799 b". United States. doi:10.1088/0004-637X/804/1/61. https://www.osti.gov/servlets/purl/1367960.
@article{osti_1367960,
title = {Simultaneous Detection of Water, Methane, and Carbon Monoxide in the Atmosphere of Exoplanet HR 8799 b},
author = {Barman, Travis S. and Konopacky, Quinn M. and Macintosh, Bruce and Marois, Christian},
abstractNote = {Here, absorption lines from water, methane, and carbon monoxide are detected in the atmosphere of exoplanet HR 8799 b. A medium-resolution spectrum presented here shows well-resolved and easily identified spectral features from all three molecules across the K band. The majority of the lines are produced by CO and H2O, but several lines clearly belong to CH4. Comparisons between these data and atmosphere models covering a range of temperatures and gravities yield log mole fractions of H2O between –3.09 and –3.91, CO between –3.30 and –3.72, and CH4 between –5.06 and –5.85. More precise mole fractions are obtained for each temperature and gravity studied. A reanalysis of H-band data, previously obtained at a similar spectral resolution, results in a nearly identical water abundance as determined from the K-band spectrum. The methane abundance is shown to be sensitive to vertical mixing and indicates an eddy diffusion coefficient in the range of 106–108 cm2 s–1, comparable to mixing in the deep troposphere of Jupiter. The model comparisons also indicate a carbon-to-oxygen ratio (C/O) between ~0.58 and 0.7, encompassing previous estimates for a second planet in the same system, HR 8799 c. Super-stellar C/O could indicate planet formation by core-accretion; however, the range of possible C/O for these planets (and the star) is currently too large to comment strongly on planet formation. More precise values of the bulk properties (e.g., effective temperature and surface gravity) are needed for improved abundance estimates.},
doi = {10.1088/0004-637X/804/1/61},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 804,
place = {United States},
year = {2015},
month = {5}
}